This is a resubmission of an earlier application. In this program, the goal is the development of a miniature electrochemical oxygen sensor of a three electrode design. The sensor will be fabricated within the bore of a small (28 gauge, .23 mm ID) hypodermic needle. The device will be protected with a cellulose acetate membrane fabricated by proprietary techniques. The device will be capable of continuously monitoring oxygen and is intended for insertion in flap or free muscle transplants after reconstructive surgery. The sensor is based on previously developed technology that has not been publically disclosed. New construction techniques that address previous size and fragility issues will be developed. Laboratory studies will be performed using oxygenation saline for routine evaluation and calf serum to test for resistance of the sensor to contamination by the interstitial fluid that comprises the ultimate operating environment PROPOSED COMMERCIAL APPLICATION: Based on the potential to indicate tissue hypoxia, albeit at a local level, this device has the potential to successfully penetrate the clinical market for detecting loss of blood flow into reconstructive surgical sites.